Power-gate transistors are used to provide gated power supply to one or more logic units (e.g., a processor core, memory block, an input-output (I/O) unit, etc). The term “gated power supply” generally refers to power supply which is controlled by a device (e.g., transistor). For example, power supply provided as output by source/drain terminal of a pass-gate when the pass-gate is turned ON is the gated power supply, while the power supply received as input by the drain/source terminal of the power-gate is the un-gated power supply.
Power-gate transistors have a gate terminal which is used to turn on or off the power-gate transistors. An un-gated power supply is provided to one of the terminals (source or drain) of the power-gate transistors and a gated power-supply is provided from the power-gate transistor as output for supplying power to logic units. Power-gate transistors are generally very large because they are designed with the ability to provide power supply to a large logic block of an integrated circuit.
In the case when the gated power supply is substantially close to ground, turning on the power gate causes gated power supply to ramp up. As the gated power supply ramps up, the gated power supply rail experiences di/dt and dv/dt events which may be mistaken for electro-static discharge (ESD) events. In such cases, ESD clamps may turn on and prematurely clamp the gated power supply and inhibit the power supply ramping process for the integrated circuit.